In response to demands for high-quality multimedia services using a wireless mobile communication technology, a next-generation radio transmission technique is needed to send more data even faster in a lower error probability.
To this end, a Multiple Input Multiple Output (MIMO) antenna is suggested. The MIMO antenna performs a MIMO operation by arranging a plurality of antenna elements in a specific structure. Thus, the MIMO antenna can raise a data rate in a certain range or extend a system range at a specific data rate. The MIMO antenna, which is a next-generation mobile communication technique of wide applications in a mobile terminal or a repeater, is attracting attention as the advanced technique for overcoming limitations on the amount of the transmission data in the exiting mobile communications due to the extension of the data communications.
However, to install the plurality of the antenna elements within a small terminal, the MIMO antenna requires smaller antenna elements. It is difficult to implement such a small antenna element using the conventional antennas. Therefore, what is needed is smaller antenna elements for the MIMO system in accordance with the miniaturization of the terminal.
Further, when a signal is received on the MIMO antenna, the channel environment also changes according to the position of the MIMO antenna. Hence, it is difficult to recover the signal because of the inconstant Received Signal Strength Indication (RSSI) of the received signal. Particularly, a linearly polarized antenna is generally installed in the receiver to correspond to an antenna which sends the linear polarized wave. If the polarized wave changes in a multi-path environment, the receiver is subject to the loss in the RSSI.
As the receiver near the transmitter receives the signal of a high correlation, the MIMO antenna may not recover the signal.